The contribution of fish to nutrition and food security: informing the evidence base for agricultural policy in Bangladesh

Abstract

BackgroundMalnutrition and poor quality diets are the leading drivers of the global burden of disease, affecting one in three people globally. Pregnant and lactating women, and infants of complementary feeding age are particularly vulnerable. The fisheries sector is well-placed to contribute to improving malnutrition and food insecurity, particularly in the context of Bangladesh, yet is often overlooked.AimsThe broad aim of this research is to understand how fish contributes to nutrition and food security, how this is changing according to broader trends in aquatic food systems, and how fisheries might be better utilised to reduce malnutrition. The focus is on nutrients known to be significant causes of malnutrition in Bangladesh: iron, zinc, calcium, vitamin A and vitamin B12. This broad aim is addressed through five specific research questions (RQs):RQ1: What is the nutritional value of commonly consumed fish in Bangladesh?RQ2: How could local nutrient-rich foods including fish, be utilised to improve nutritional quality of diets?RQ3: What does fish currently contribute to diets in terms of nutrient intakes?RQ4: How has the transition in aquatic food systems (declining availability of species from capture fisheries, and rapid growth in aquaculture) impacted nutrient intakes?RQ5: How could nutritional quality of fish production systems be measured and used in decision making?MethodsThis research draws on a variety of different methods to address individual RQs. The nutritional value of fish (RQ1) was determined by primary analysis of 55 fish species for composition of protein, fat and selected minerals, vitamins and essential fatty acids using standard analytical methods. Raw, edible parts of individual samples were homogenised then analysed in duplicate. The use of fish to improve diets among vulnerable groups (RQ2) was informed by a review of local food-based approaches including food processing methods, and nutrient composition of local ingredients, followed by laboratory based trial production of recipes. The role of fish in current diets (RQ3) was informed through secondary analysis of intra-household food consumption data (based on 24-hour recall) of a two-stage stratified nationally representative survey of rural Bangladesh (n=5,503 households, 24,198 individuals). Linear regression was used to estimate mean fish consumption, controlling for age, sex, wealth group and geographic region (adjusted by sampling weights). The impact of a shift in fish consumption away from non-farmed towards farmed fish, on nutritional quality of diets (RQ4) was estimated through secondary analysis of food consumption data from nationally representative household income and expenditure surveys in 1991 (n=5,745), 2000 (n=7,440) and 2010 (n=12,240). Linear regression, adjusting for sampling weights and clustering in survey design, was used to estimate mean fish consumption among different population groups. Measurement of nutritional quality of fish production systems (RQ5) was informed through a review of existing indicators and comparison of their strengths and limitations applied to common homestead pond aquaculture systems in Bangladesh.Main findingsThe nutrient composition of fish varies widely across species, particularly for micronutrients. Iron content ranged from 0.34-19 mg/100 g raw, edible parts; zinc from 0.6-4.7 mg/100 g; calcium from 8.6-1900 mg/100 g; vitamin A from 0-2503 mg RAE/100 g; and vitamin B12 from 0.50-14 mg/100 g. Non-farmed fish contribute between 6-35% of daily recommended nutrient intakes for iron, zinc, calcium, vitamin A and vitamin B12, more than farmed fish, despite being consumed in smaller portions (Pl0.0001); and are therefore better placed to contribute to improved micronutrient intakes among vulnerable groups. Adaption of traditional recipes to include these nutrient-rich fish, combined with other local nutrient-rich foods and using simple processing methods, shows great potential to improve nutrient intakes. For example, consumption of the proposed complementary food product could meet g60% of the daily vitamin A and zinc needs for a child. However, such nutrient-rich species are not the current focus of production policies. Aquaculture systems are designed to maximise yields without considering nutritional quality. Growth in aquaculture has allowed fish consumption to increase nationally by 30% between 1991 and 2010, despite a 33% decline in availability of non-farmed fish. However, increased reliance on farmed fish of lower nutritional quality, has led to an overall decrease in micronutrient intakes from fish: iron significantly decreased by 15% (Pl0.01), calcium by 14% (Pl0.01), and zinc, vitamin A andnvitamin B12 remained unchanged despite an increase in total quantity of fish being consumed.ConclusionsFisheries make an important but undervalued contribution to nutrition and food security in Bangladesh. However, the current policy focus on maximising quantity of production from this sector, without considering quality, has had negative impacts on nutritional quality of diets. A nutrition-sensitive approach to fisheries policy is necessary. Such an approach would enable the fisheries sector to make a more substantial contribution to the reduction of malnutrition and food insecurity in Bangladesh. These findings are of great relevance to other countries experiencing this transition in aquatic food systems and malnutrition.